1. Field of the Invention
The present invention relates to a method for producing a liquid discharge recording head for discharging liquid droplets, adapted for use in a liquid discharge recording apparatus which effects recording by discharging droplets of recording liquid such as ink from discharge openings and depositing said liquid droplets onto a recording medium such as paper.
2. Related Background Art
The liquid discharge recording head employed in the liquid discharge recording (ink jet recording) is generally provided with fine liquid discharge apertures (orifices), liquid paths and energy generating units for liquid discharge, provided in a part of said liquid paths. For producing such recording head, there is known a method as disclosed in the Japanese Patent Laid-open Application Nos. 61-154947 and 62-253457, which will be explained in the following with reference to FIG. 1
At first, on a substrate 1, there is formed a layer of photosensitive resin (positive photoresist) 2 (FIG. 1A). The substrate is composed for example of glass, ceramics, plastics or metal, and is provided, in desired positions thereon, with a desired number of liquid discharge energy generating elements such as electrothermal converters or piezoelectric elements, and with wirings for connecting said elements with control signal input electrodes for activating said elements. Then the photosensitive resin layer on the substrate 1 is exposed to light through a mask 3 (FIG. 1B), and is patterned by development, whereby a solid layer is formed on the substrate (FIG. 1C). Then the patterned solid layer is covered with a liquid path forming material 5 curable with an actinic energy ray (FIG. 1D), and the material is cured by the irradiation with actinic energy ray (FIG. 1E). Finally the patterned solid layer is dissolved with an organic solvent such as halogenated hydrocarbon, ketone, ester, ether or alcohol, or aqueous alkali solution such as of sodium hydroxide or potassium hydroxide, whereby liquid paths 6 are formed (FIG. 1F).
The above-explained method generally employs, as the photosensitive resin material for forming the solid layer, positive photoresist containing a naphthoquinone diazide derivative. Said naphthoquinone diazide derivative, employed in the positive photoresist, is known to generate nitrogen gas, according to the following chemical reaction, under the light irradiation in air at room temperature: ##STR1##
As indene carboxylic acid generated by the above-mentioned reaction is easily soluble in aqueous alkali solution, the exposed area can be easily removed with aqueous alkali solution, whereby the patterning can be achieved.
On the other hand, if the liquid path forming material, to be coated on the patterned solid layer, is curable with light, there is required flush exposure for curing of said material. In such flush exposure, the exposing light also reaches the patterned positive photoresist, thus inducing the above-mentioned reaction and generating nitrogen gas therein. Since the photosensitivity of positive photoresist is generally higher than that of the light-curable material, the nitrogen gas generated from the positive photoresist intrudes the liquid path forming material provided on the patterned photoresist and remain as bubbles in said material when it is cured. For this reason, there are encountered drawbacks of deformation of the liquid paths finally formed by the removal of the patterned positive photoresist, and a lowered strength of the recording head, eventually leading to the breakage thereof.